Aromatic Ring Overlap Pedals the Nature of Exciton Coupling and Carrier Transport in a Series of Electron-Deficient Anthracenes

Abstract

Planar aromatic semiconductors are excellent active layer materials for charge transport (mostly p-type) and light emission in various organic electronic devices. The exciton coupling is well known for controlling the optical traits of such materials in the bulk state. In terms of the carrier mobility, to achieve ambipolar transport in these classes of materials, the frontier molecular orbital energy levels should be appropriately engineered. Core functionalization using a moderately strong electron-withdrawing group (such as −CF3) could be a potential strategy to obtain appropriate energy levels. Herein, we have selected positional isomers of the bis–CF3 substituted derivatives as the possible group of molecules. In the bulk film state, depending on the spatial overlap of the aromatic core unit, distinct optical traits of the J- and H-type excitonically coupled dimeric states were evident in these series. Prominent enhancement of the radiative rate constant (and photoluminescence quantum yield) in J-type dimers (first pair of molecules) and substantially quenched excimer state emission for the H-type dimers was evident for the other pair in the solid-state samples. At the same time, in contradiction to the general perception of significant aromatic overlap for higher carrier mobility, the derivative with the highest spatial overlap had the least among the four products. An analogy could be drawn between the aromatic overlap in the solid-state dimers with their optical and the charge carrier mobility. Detailed experimental outcomes and the analysis are discussed in the present article.

Preparation of different conjugated polymers characterized by complementary electronic properties from an identical precursor

“…35,36 Anthracene-based materials have often been proposed for applications in optoelectronics, including OPV devices, 37,38 OLEDs, 39,40 OFETs 41,42 and sensing, 43 as they can be particularly useful in those cases for which a medium bandgap is needed. 44 Alternatively, by removing the acetylide moiety under retro-Favorskii conditions, it is possible to prepare a polymer bearing anthraquinone units (AQ-P, Fig. 1a), i.e., characterized by a lowenergy LUMO level and a cross-conjugated framework.…”

“…Anthracene-based materials have often been proposed for applications in optoelectronics, including OPV devices, 37,38 OLEDs, 39,40 OFETs 41,42 and sensing, 43 as they can be particularly useful in those cases for which a medium bandgap is needed. 44…”

Charge Transport through Discrete Crystalline Architectures

“…The discrete packing arrangements in organic chromophores are dictated by numerous noncovalent interactions. Introduction of heteroatom/functional groups to hydrocarbon backbone can induce change in condensed phase architecture by creating additional interactions. Consequently, heteroatom doping will have an impact on the charge transport properties in the crystalline state. , Nitrogen doping in wing-shaped tetrabenzoacene (TBA) derivatives has reduced the interplanar distance through N···C interactions .…”

Intramolecular Charge Transfer and Stimuli-Responsive Emission in Cholesterol-Appended Phenothiazine–Cyanostyryl-Based Donor–Acceptor Systems

“…Organic luminogens designed from π-conjugated molecules have been explored for numerous applications in the field of purely organic optoelectronic devices, including organic light-emitting diodes (OLED), , organic light-emitting field-effect transistors (OLEFETs), , and flat panel displays. , The luminogens based on π-conjugated molecules have been investigated for their applications as fluorescent sensors, switches, , and stimuli-responsive materials. − Most of the optoelectronic applications call for highly emissive and stable solid organic materials with ease in synthesis and processability. Although most of the π-conjugated organic systems are highly emissive in solution, they are weakly emissive or nonemissive in the solid state due to the π–π stacking-induced quenching .…”